Flexible intumescent coating composition

ABSTRACT

Disclosed is an intumescent curable composition which contains as a resinous binder a flexible polyepoxide resin. The polyepoxide is cured with an appropriate curing agent adapted for the particular resin. An additive component is present which contains a mixture of materials which provide a source of 
     (i) zinc, 
     (ii) boron, 
     (iii) phosphorus, and 
     (iv) an expansion gas upon thermal decomposition. The composition is capable of forming a carbonaceous char upon exposure to heat or flame, with the proviso that the cured, unburned composition has sufficient flexibility that is passes at least 10 continuous cycles of a cold cycle test without cracking. The cold cycle test involves the following steps: the composition is applied at a thickness of 0.5 inch (12.7 millimeters) to a 10 inch (0.0254 meter) section of a 4W13 I-beam having two thermocouples attached to the surface, allowed to cure at ambient temperature for 16 hours, force cured for 5 days at about 60° C. and subjected to the cold cycle test. For one cycle, the beam is placed in a freezer operating at a temperature between about 0° F. (-18° C.) and about -10° F. (-23° C.) for sufficient time for the steel to reach a temperature between about 0° F. (-18° C.) and about (-10° F.) -23° C. as determined by the two thermocouples attached to the surface of the beam beneath the coating, removed from the freezer and a 50 square inch area (0.0323 square meter) of the surface warmed as shown in FIGS. 1 and 2 by passing a heat gun (Model No. HG 50146, Alpha Division of Loral Corp., 14 amp: minimum temperature at tip 500° F. (260° C.)) a distance of 0.5 inch (12.7 millimeter) from the surface, uniformly over the surface until the surface temperature reaches 110° F. (43° C.) within a 3 minute period, as determined by a thermocouple moved about the surface and allowed to stand for at least 2 hours at ambient temperature.

BACKGROUND OF THE INVENTION

The present invention relates to fire protective intumescent curablecompositions.

Over the years, intumescent compositions have been utilized for avariety of structural applications including columns, I-beams, girders,bulk-heads and a variety of other structural building components. A veryimportant requirement of these compositions is the ability to uniformlyform a carbonaceous char during a fire which will adhere to thesubstrate without cracking. In addition, it is very important that theunburned composition adhere well to the substrate without cracking inorder to protect the underlying substrate from damage brought about byclimatic exposure and also for the composition to be in good conditionshould a fire occur. A composition which is already cracked in theunburned state provides a diminished level of protection to theunderlying substrate once it burns and forms a char since there is agreater likelihood that the char formed during a fire will fall from thesubstrate leaving it unprotected.

A major cause of cracking in the unburned state is the climaticconditions to which the composition is exposed. For example, dramatictemperature shifts from very hot to very cold within a short period oftime such as over the course of a day contribute to stresses within thecomposition which may lead to cracking.

There is a need, therefore, for a curable intumescent composition whichis capable of adhering to a substrate without cracking in the unburnedstate, even when exposed to extreme changes in temperature and weatherconditions; and in addition which is capable of intumescing to form auniform carbonaceous char upon exposure to heat or flame therebyprotecting the underlying substrate from the structural damage which maybe brought about by a fire.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided aintumescent curable composition comprising:

(a) a polyepoxide resin,

(b) a curing agent adapted to cure the polyepoxide resin,

(c) an additive component comprising a mixture of materials adapted toprovide a source of

(i) zinc,

(ii) boron,

(iii) phosphorus and

(iv) an expansion gas upon thermal decomposition, said composition beingcapable of forming a carbonaceous char upon exposure to heat or flame,with the proviso that the cured, unburned composition has sufficientflexibility that it passes at least 10 continuous cycles of a cold cycletest without cracking when the composition is applied at a thickness of0.5 inch (12.7 millimeters) to a 10 inch (0.254 meter) section of a 4W13I-beam having two thermocouples attached to the surface, allowed to cureat ambient temperature for 16 hours, force cured for 5 days at about 60°C. and subjected to the cold cycle test wherein for one cycle the beamis placed in a freezer operating at a temperature between about 0° F.(-18° C.) and about -10° F. (-23° C.) for sufficient time for the steelto reach a temperature between about 0° F. (-18° C.) and about (-10°F.) - 23° C. as determined by the two thermocouples attached to thesurface of the beam beneath the coating, removed from the freezer and a50 square inch area (0.0323 square meter) of the surface warmed as shownin FIGS. 1 and 2 by passing a heat gun (Model No. HG 50146, AlphaDivision of Loral Corp, 14 amp: minimum temperature at tip 500° F. (260°C.)) a distance of 0.5 inch (12.7 millimeter) from the surface,uniformly over the surface until the surface temperature reaches 110° F.(43° C.) within a 3 minute period, as determined by a thermocouple movedabout the surface, and allowed to stand for at least 2 hours at ambienttemperature.

Also provided in accordance with the present invention is a substratewhich demonstrates a reduced rate of temperature rise when it issubjected to fire conditions.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an isometric view of a ten (10) inch section of a 4W13 I-beam.The shaded area represents the area of the beam heated with a heat gunduring the cold cycle test.

FIG. 2 is a top view of FIG. 1. The direction of heating is shown by thepath marked with arrows (15).

DETAILED DESCRIPTION OF THE INVENTION

An intumescent curable composition according to the present inventioncomprises a polyepoxide resin, a curing agent adapted to cure thepolyepoxide resin, and an additive component which comprises a mixtureof materials adapted to provide a source of zinc, boron, phosphorus andan expansion gas upon thermal decomposition. The composition is capableof forming a carbonaceous char upon exposure to heat or flame and hassufficient flexibility when cured to pass at least 10 continuous cyclesof a cold cycle test which is described more fully below, withoutcracking. The cold cycle test has been observed to be an excellentpredictor of the flexibility of the claimed compositions when exposed toextreme temperature changes within a short time period.

The cold cycle test is conducted in the following manner. The testsubstrate, a 10 inch section (0.254 meter) of 4W13 I-beam, is readied byattaching two thermocouples to the surface, each centrally located, in amanner and specific location as described below. The intumescent curablecomposition is uniformly applied to the I-beam at a thickness of 0.5inch (12.7 millimeters), covering both thermocouples. The coated beam isthen allowed to stand at ambient temperature (23° C.) for 16 hours inorder for the intumescent composition to cure. Thereafter, the coatedbeam is maintained at a temperature of 60° C. for 5 days to force curethe applied coating.

The beam is then subjected to the cold cycle test. One complete cycle ofthe test involves the following steps. The beam is placed in a freezeroperating at a temperature between 0° F. (-18° C.) and about -10° F.(-23° C.) for sufficient time for the steel to reach a temperaturebetween about 0° F. (-18° C.) and about -10° F. (-23° C.), as determinedby the two thermocouples attached to the surface of the beam beneath thecoating. The beam is removed from the freezer and immediately thereaftera 50 square inch area (0.0323 square meter) of the surface is warmed bypassing a heat gun uniformly over the surface as shown by the shadedarea in FIG. 1 and FIG. 2. For the sake of simplicity, the figures onlyshow the metal core of the beam 10. The layer of intumescent coatingcomposition which is present is admitted but eliminated for ease ofdiscussion. With reference to FIG. 1 and FIG. 2, thermocouples 18 and 20are placed at adjacent corners of the outer legs 12 and 14 which areseparated by web 16, opposite and diagonal to one another. Moreparticularly, in outer leg 12, thermocouple 18 is placed at a depth ofthree (3) inches into the leg. In outer leg 14, thermocouple 20 isplaced at a depth of three (3) inches into the leg. The path followed bythe heat gun in warming the surface is shown by the arrows 15 in FIG. 2.A suitable heat gun is a Model No. HG 50146 manufactured by the AlphaDivision of Loral Corporation, rated for 14 amperes and heating to aminimum temperature of 500° C. (260° C.) at the tip. Also suitable areheat guns which provide comparable specifications. The gun is heldapproximately 0.5 inch (12.7 millimeters) from the surface and passeduniformly over the surface until the surface temperature reaches 110° F.(43° C.) within a 3 minute period. The surface temperature is monitoredby a thermocouple which is moved about the surface. The beam is thenallowed to stand for at least 2 hours at ambient temperature whichconcludes one complete cycle of the cold cycle test.

The coating compositions of the present invention have sufficientflexibility in the cured, unburned state that they are capable ofpassing at least 10 continuous cycles of the aforedescribed cold cycletest without cracking.

Preferably, the claimed coating compositions have sufficient flexibilityto pass at least 30 continuous cycles, more preferably at least 50continuous cycles and most preferably at least 70 continuous cycles.

Preferably, the claimed intumescent curable compositions are preparedwith a flexible polyepoxide resin. These resins are generallyessentially linear materials, although a small amount of branching istolerated. Exemplary of suitable materials are epoxidized soybean oil,dimer acid based materials such as EMPOL 1010 resin which iscommercially available from Emery Chemicals and rubber modifiedpolyepoxide resins such as the product prepared from a polyglycidylether of bisphenol A, e.g. EPON 828 from SHELL Chemical, and an acidfunctional polybutadiene.

Alternatively, in one embodiment, a flexible curing agent can beutilized. One example of such a material is commercially available fromB.F. Goodrich, amine terminated butyl-N-rubber (sold as ATBN). One wayof preparing a flexible curing agent is by the addition of aflexibilizer to the curable composition which is reactive with thecuring agent. For example, urethane acrylate copolymers are particularlysuitable for modification of amine functional curing agents. Theurethane acrylate copolymers are capable of reacting with the aminogroups by a Michael addition reaction.

One particularly preferred example of a flexible polyepoxide for useherein is an epoxy functional adduct which is prepared from a flexibleacid functional polyester and polyepoxide.

The acid functional polyester generally has an acid value of at leastabout 10 mg KOH/g, generally from about 140 to about 350 mg KOH/g andpreferably from about 180 to about 260 mg KOH/g, as determined by ASTM974-87.

Linear polyesters are more preferred than branched polyesters for useherein. Acid functional polyesters can be prepared by thepolyesterification of an organic polycarboxylic acid or anhydridethereof with an organic polyol. Usually, the polycarboxylic acids andpolyols are aliphatic or aromatic dibasic acids and diols.

The diols which are usually employed in making the polyester includealkylene glycols, such as ethylene glycol, diethylene glycol, neopentylglycol and other glycols such as hydrogenated Bisphenol A,cyclohexanediol, cyclohexanedimethanol, caprolactonediol, for example,the reaction product of epsilon-caprolactone and ethylene glycol,hydroxy-alkylated bisphenols, polyether glycols, for example,poly(oxytetramethylene) glycol and the like. Polyols of higherfunctionality can also be used, although diols are preferred. Examplesinclude trimethylolpropane, trimethylolethane, pentaerythritol,glycerine and the like, as well as higher molecular weight polyols suchas those produced by oxyalkylating lower molecular weight polyols.

The acid component of the polyester consists primarily of monomericdicarboxylic acids or anhydrides having 2 to 36 carbon atoms permolecule. Among the acids which are useful are phthalic acid,isophthalic acid, terephthalic acid, tetrahydrophthalic acid,hexahydrophthalic acid, adipic acid, azelaic acid, sebacic acid, maleicacid, glutaric acid, chlorendic acid, tetrachlorophthalic acid,tetrabromophthalic acid, decanedioic acid, dodecanedioic acid, and otherdicarboxylic acids of varying types, for example, Diels-Alder adducts ofunsaturated C₁₈ fatty acids such as the product sold by West-Vaco Co.under the trademark DIMER ACID. The polyester may include minor amountsof monobasic acids such as benzoic acid, stearic acid, acetic acid,hydroxystearic acid and oleic acid. Also, there may be employed higherpolycarboxylic acids such as trimellitic acid. Where acids are referredto above, it is understood that anhydrides of those acids which formanhydrides can be used in place of the acid. Also, lower alkyl esters ofthe acids such as dimethyl glutarate and dimethyl terephthalate can beused.

In a preferred embodiment of the present invention, the polyester usedto prepare the epoxy functional adduct is prepared from a polycarboxylicacid component comprising a polycarboxylic acid or mixture of acidshaving from 7 to 16 carbon atoms and a polyol component comprising aportion of diethylene glycol. For example, one preferred embodimentutilizes a mixture of dodecanedioic acid and azeleic acid as the acidcomponent.

The polyepoxide used to prepare the epoxy functional adduct can bealiphatic, aromatic, cyclic, acyclic, alicyclic or heterocyclic.Generally, the epoxide equivalent weight ranges from about 100 to about1780, preferably 120 to 250, more preferably 125 to 195. Preferably,aromatic epoxide resins are used herein.

One particularly preferred group of aromatic epoxy resins are thepolyglycidyl ethers of polyhydric aromatic alcohols, such as, forexample, dihydric phenols. The phenol must be at least dihydric andsuitable examples include resorcinol, catechol, hydroquinone,bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenyl)-1, 1-ethane; bis(2-hydroxynaphenyl)methane;1,5-hydroxynaphthalene and 4,4'-isopropylidene-diphenol, i.e., bisphenolA. Preferably bisphenol A is utilized. Of the many epoxy compoundspossible, the one principally utilized is epichlorohydrin althoughepibromohydrin is also quite useful. The polyglycidyl ethers especiallyuseful herein are obtained by reacting epichlorohydrin and bisphenol Ain the presence of an alkali such as sodium or potassium hydroxide. Theseries of epoxy resins sold by Shell Chemical Company under thetrademark EPON are especially useful herein.

Another group of useful epoxy resins are the polyglycidyl ethers derivedfrom such polyhydric alcohols as ethylene glycol; diethylene glycol;triethylene glycol; 1,2-propylene glycol; 1,4-butylene glycol;1,5-pentanediol; 1,2,6-hexanetriol; glycerol and trimethylolpropane. Ofthis group, the polyglycidyl ethers of 1,4-butylene glycol arepreferred. Examples of these include RD-2 commercially available fromCiba-Geigy and HELOXY WC-67 from Wilmington Chemical Company.

Also useful are the epoxide resins which are polyglycidyl ethers ofpolycarboxylic acids. These materials are produced by the reaction of anepoxy compound such as epichlorohydrin with an aliphatic or aromaticpolycarboxylic acid such as oxalic acid; succinic acid; glutaric acid;terephthalic acid; 2,6-napthalene dicarboxylic acid and dimerizedlinoleic acid.

Still another group of epoxide resins are derived from the epoxidationof an olefinically unsaturated alicyclic material. Among these are theepoxy alicyclic ethers and esters well known in the art.

Besides the materials discussed above, useful epoxy resins also includethose containing oxyalkylene groups. Such groups can be pendant from thebackbone of the epoxide resin or they can be included as part of thebackbone. The proportion of oxyalkylene groups in the epoxy resindepends upon a number of factors, among them, the size of theoxyalkylene group and the nature of the epoxy resin.

One additional class of epoxy resins encompasses the epoxy novolacresins. These resins are prepared by reacting an epihalohydrin with thecondensation product of an aldehyde with a monohydric or polyhydricphenol. One example is the reaction product of epichlorohydrin with aphenol-formaldehyde condensate. A mixture of epoxy resins can also beused herein.

The acid functional polyester and the polyepoxide are reacted in amountssuch that residual epoxy functionality remains. The epoxy equivalentweight of the epoxy functional adduct generally ranges from about 250 toabout 600, preferably from about 350 to about 450.

The aforedescribed epoxy functional adduct requires the addition of acuring agent in order to convert it to a cured material. Curing can takeplace either at ambient temperature or upon application of heat. Ingeneral, the curing agents which can be utilized herein can be selectedfrom a variety of materials, for example, amine type, includingaliphatic and aromatic amines, and poly(amine-amides). Examples of theseinclude diethylene triamine; 3,3-amino bis propylamine; triethylenetetraamine; tetraethylene pentamine; m-xylylenediamine; and the reactionproduct of an amine and an aliphatic fatty acid such as the series ofmaterials sold by Henkel under the trademark VERSAMID. Preferably thepoly(amine-amide) materials such as VERSAMID or its equivalent areutilized.

Also suitable as curing agents are polycarboxylic acids andpolycarboxylic acid anhydrides. Examples of polycarboxylic acids includedi-, tri-, and higher carboxylic acids such as, for example, oxalicacid, phthalic acid, terephthalic acid, succinic acid, alkyl andalkenyl-substituted succinic acids, tartaric acid, and polymerized fattyacids. Examples of suitable polycarboxylic acid anhydrides include,among others, pyromellitic anhydride, trimellitic anhydride, phthalicanhydride, succinic anhydride, and maleic anhydride.

Other suitable curing agents include boron trihalide and complexes ofboron trihalide with amines, ethers, phenols and the like;polymercaptans; polyphenols; metal salts such as aluminum chloride, zincchloride and magnesium perchlorate; inorganic acids and partial esterssuch as phosphoric acid and n-butyl orthophosphite. It should beunderstood that blocked or latent curing agents can also be utilized ifdesired; for example, ketimines which are prepared from a polyamine anda ketone, and aldimines which are prepared from a polyamine and analdehyde.

Also suitable for use herein as a curing agent for the epoxy functionaladduct is an amine functional Michael adduct prepared from componentscomprising a mono-, di- or polyfunctional amine or mixtures thereof anda mono-, di- or polyfunctional acrylate or mixtures thereof. The amineis used in excess to the acrylate. The molar ratio of amine to acrylateused in preparing the Michael adduct generally ranges from about 2:1 toabout 1.2:1, preferably from about 1.5:1 to about 1.33:1.

Examples of suitable monoamines include ethanolamine, methylethanolamine, isopropanolamine, aniline, n-butyl amine, 2-aminohexane,cyclobutylamine and 2-ethylhexylamine.

Useful di- and polyfunctional amines include hydrazine, ethylenediamine, 1,3-propylene diamine, 1,4-butylene diamine, 1,5-diaminopentane, 1,6-hexamethylene diamine, 1,2-cyclohexamethylene diamine,1,4-diamino cyclohexane, 1,4-phenylene diamine, meta-xylene diamine,isophorone diamine, 2,4-toluene diamine, trimethyl 1,6-hexamethylenediamine menthane diamine, triethylene glycol diamine and variouspolyoxypropylene diamines which are commercially available from Texacounder the trademark JEFFAMINE, e.g., JEFFAMINE D-230, D-400, D-500. Inaddition bishexamethylene triamine; diethylene triamine; dipropylenetriamine; polyoxypropylene triamine; triethylene tetramine;tetraethylene pentamine; 2,4-bis(para-aminobenzyl) aniline, aminoethylpiperazine, bis(aminopropyl)piperazine and tris(2-aminoethyl)amine.

Examples of monofunctional acrylates include acrylonitrile, methylacrylonitrile, acrylamide, N-methylolacrylamide, hydroxyethyl acrylateand hydroxypropyl acrylate. Examples of di- and polyfunctional acrylatesinclude diacrylates of 1,4-butanediol, neopentyl glycol, ethyleneglycol, 1,2-propanediol, 2,2,4-trimethyl- 1,3-pentanediol,1,6-hexanediol, 2,2-dimethyl-3-hydroxypropyl2,2-dimethyl-3-hydroxy-propionate and diols containing a cyclicstructure such as 1,4-cyclohexane dimethanol, para-xylene glycol, and1,4-cyclohexane diol. In addition, the triesters of acrylic acid withtrimethylolethane, trimethylolpropane and pentaerythritol.

The amount of epoxy functional adduct and curing agent can vary, butgenerally, in the instance of the amine curing agents, the equivalentratio of epoxy to amine is within the range of from about 0.05:1 toabout 10:1. Preferably, the epoxy to amine equivalent ratio is withinthe range of from about 0.1:1 to 2:1 and more preferably within therange of 0.3:1 to 0.9:1.

The additive component of the claimed intumescent composition comprisesa mixture of materials adapted to provide a source of phosphorus, zinc,boron, and an expansion gas upon thermal decomposition. In a preferredembodiment the additive component additionally contains a reinforcingfiller.

The source of phosphorus can be selected from a variety of materialssuch as, for example, phosphoric acid, mono- and di-ammonium phosphate,tris-(2-chloroethyl)phosphate, phosphorus-containing amides such asphosphorylamide, and melamine pyrophosphate. Preferably the source ofphosphorous is an ammonium polyphosphate represented by the formula:

    (NH.sub.4).sub.n+2 P.sub.n O.sub.3n +1

wherein n is an integer of at least 2, preferably n is an integer of atleast 50. Examples of such materials are those commercially availableunder the trademark designations PHOS-CHEK-P-30 from MonsantoCorporation, and AMGARD MC from Albright and Wilson Corporation.Preferably, PHOS-CHEK-P-30 is utilized herein. The claimed intumescentcomposition typically contains an amount of phosphorous which rangesfrom about 0.05 to about 20 percent by weight, preferably 0.5 to 10percent by weight, the percentages being based upon the total weight ofthe epoxy resin, curing agent, and the additive component. Thephosphorus is believed to function as a char promoter in the intumescentcomposition.

The expansion gas serves to cause the fire protective composition tofoam and swell, i.e., intumesce, when exposed to high temperatures orflames. As a result of this expansion the char which is formed is athick, multicelled material which serves to insulate and protect theunderlying substrate. Preferably, the source of expansion gas is anitrogen-containing material. Examples of suitable nitrogen-containingmaterials include melamine, methylolated melamine, hexamethoxymethylmelamine, urea, dimethylurea, melamine pyrophosphate, dicyandiamide,guanylurea phosphate and glycine. Preferably, melamine is utilized.Other conventional sources of expansion gas can also be used such asthose materials which liberate carbon dioxide. The source of expansiongas is usually present in the compositions of the present invention inan amount ranging from 0.1 to 25 percent by weight, preferably 1 to 10percent by weight, the percentages being based upon the total weight ofthe epoxy resin, curing agent, and the additive component.

The source of zinc can be selected from a variety of materials. It isbelieved that the zinc material contributes to the formation of asmall-celled structure in the char. The small cells of the char affordbetter insulation for the substrate and are better able to retain thechar's integrity and adhere to the substrate even in the absence ofexternal reinforcing materials. Thus, cracking of the char and itsbreaking away from the substrate are minimized and a greater measure ofprotection is afforded to the underlying steel. Examples of suitablematerials which are sources of the zinc include zinc oxide, zinc saltssuch as zinc borate and zinc phosphate; zinc carbonate; also zinc metalcan be used. Preferably, zinc borate is utilized. Usually the claimedintumescent composition contains an amount of zinc which ranges fromabout 0.1 to 25 percent by weight, preferably 0.5 to 12 percent weight,the percentages being based upon the total weight of the epoxy resin,curing agent and the additive component.

The source of boron is preferably ammonium pentaborate or zinc boratealthough a large variety of other materials can be utilized. Examples ofsuitable materials which can provide boron include boron oxide, boratessuch as sodium borate, potassium borate and ammonium borate, also borateesters such as butyl borates or phenyl borates. The claimed intumescentcomposition usually contains an amount of boron with ranges from about0.1 to 10 percent by weight, preferably 1 to 6 percent by weight, thepercentages being based upon the total weight of the epoxy resin, curingagent and the additive component.

It should be understood that the phosphorus, zinc, boron, and expansiongas can each be provided by a separate source material or alternativelya single material may be a source of more than one of the aforelistedelement. For example, melamine pyrophosphate can provide a source ofboth phosphorus and expansion gas.

The reinforcing filler when presently the additive component can bechosen from among a large array of conventionally utilized materialsincluding fibrous reinforcements and platelet reinforcements which arepreferred over other fillers. Examples of fibrous reinforcements includeglass fibers, ceramic fibers, e.g., aluminum oxide/silicon oxide, andgraphite fibers. Platelet reinforcements include hammer-mill glassflakes, mica, and wollastonite. Other suitable fillers include clay,talc, silica, and various pigments. Preferably, wollastonite isutilized. The reinforcing filler is believed to assist in controllingexpansion of the fire protective composition prior to and during charformation so that the resultant char is hard and uniform. When present,the reinforcing filler is usually present in the composition in anamount ranging from about 1 to 50 percent by weight, the percentagesbeing based upon the total weight of the epoxy adduct, curing agent andthe additive component.

The fire protective intumescent composition of the present invention ispreferably a two-package system with the epoxy adduct in one package,the curing agent in a second package and the additive component ineither the epoxy resin package or the curing agent package or in bothpackages. When the additive component is present in both packages theindividual constituents can be in either package, as desired. Theindividual packages are mixed prior to use such that the epoxy to amineequivalent ratio in the resultant composition is within the broad rangeset forth above. The intumescent composition of the present inventioncan also be prepared as a single-package system. In this situation ablocked or latent curing agent would be preferred such as, for example,the ketimine curing agents which have been mentioned above. The ketimineblocked curing agents cure as a result of exposure to moisture whichcauses hydrolysis of the ketimine and release of the free amine curingagent. Other latent curing agents can also be utilized such as those inwhich the free amine curing agent is liberated as a result of exposureto radiation.

The composition of the present invention can also contain a variety ofconventional additives such as stabilizers, rheology control agents,flame spread control agents, and the like. These ingredients are, ofcourse, optional and can be added in varying amounts.

The intumescent curable composition of the present invention when it isprepared is usually in the form of a thick material such as a mastic. Itis preferred that the composition be solvent free and spray applied. Ifdesired, thinning can be accomplished with a variety of conventionalsolvents such as methylene chloride or 1,1,1-trichloroethane.

The intumescent curable compositions of the present invention areparticularly advantageous in that they can be applied to a variety ofsubstrates particularly steel substrates and when subjected to extremevariations in temperature over a short period of time do not exhibitcracking. The absence of cracking results in improved adhesion of thecomposition to the substrate. This ultimately enhances the protection ofthe substrate should a fire occur. A cured coating in the unburned statewhich is crack-free is better able to remain adhered to the substrateupon burning and forming a char. Therefore, the claimed compositions areparticularly advantageous in providing a substrate which demonstrates areduced rate of temperature rise when it is subjected to fireconditions.

The following examples are intended to be illustrative of the inventionand are not intended to be limiting.

EXAMPLE A Flexibilized Epoxy Resin

This example illustrates the preparation of the flexibilized epoxyresin.

Into a 5,000 ml 4-neck round bottom flask were charged 235 g of azelaicacid¹, 265 g of diethylene glycol², 862.5 g dodecane dioic acid³ and 2.7g of butyl stannoic acid⁴. The flask was equipped with a nitrogenblanket and an air motor using a paddle blade stirrer. The contents ofthe flask were heated over a period of 20 minutes to 121° C. at whichtemperature the contents of the flask were sufficiently melted to startthe agitation and to begin the nitrogen sparge. The flask was fittedwith a glycol recovery condenser, a Dean-Stark trap and a cold watercondenser. The reactants were heated over a period of 5 hours and 15minutes to 175° C. during which time distillate (water) was removed andthe acid value was followed. The reaction was held at 175° C. for anadditional 2 and 1/2 hours until the acid value reached 217. At thispoint the reaction was cooled to 100° C., and 650 g of Heloxy WC-67⁵,1800 g Epon 828⁶ and 11.3 g ethyl triphenyl phosphonium iodide⁷ wereadded. Following a moderately exothermic reaction, the temperature ofthe reaction was adjusted to 90° C. and held for 5 hours at which timethe acid value was 0.23. The flexibilized epoxy resin was then pouredinto a can and saved for future use.

EXAMPLE B Urethane Acrylate

This example illustrates the preparation of a urethane acrylate.

Into a 5,000 ml 4-neck round bottom flask was charged 1218 g of toluenediisocyanate (mixed isomers)¹. The flask was equipped with an air sparge(dry air) and an air motor using a paddle blade stirrer. The contents ofthe flask were heated to 30° C. and a solution of 1.4 g methylhydroquinone² in 812 g 2-hydroxy ethyl acrylate³ was slowly added over aperiod of 34 minutes while maintaining the reaction temperature in the30°-35° C. range with a water-ice bath. The reaction mixture was heldfor 30 minutes at 35°-40° C., then 0.3 g of dibutyltin dilaurate⁴ wasadded and the reaction mixture held for 1 hour at 60°-65° C. Over aperiod of 5 minutes, 698.4 g of tetramethylene glycol⁵ was added andallowed to exotherm for 1/2 hour while keeping the temperature below100° C. The reactants were then held at 100° C. for 5 hours and 20minutes at which time an IR Spectrum showed a small NCO peak. Anadditional 2.3 g of methyl hydroquinone was added to the reactionmixture followed by 1821.7 g of tetraethylene glycol diacrylate⁶. Aftermixing, the product was poured into a can and saved for future use.

EXAMPLE 1

This example illustrates the preparation and testing of a preferred fireprotective intumescent curable composition of the present invention.This example utilized a flexibilized polyepoxide.

    ______________________________________                                                                Parts by Weight                                       Ingredients             (grams)                                               ______________________________________                                        Package 1:                                                                            Flexibilized epoxy.sup.1                                                                          29.39                                                     EPON 828.sup.2      9.58                                                      Tris(2-chloroethyl) phosphate.sup.3                                                               13.47                                                     ATTAGEL-50.sup.4    1.50                                                      Thixatrol ST.sup.5  1.50                                                      PHOS-CHEK-P-30.sup.6                                                                              3.98                                                      Ammonium Pentaborate                                                                              8.41                                                      Zinc borate.sup.7   15.14                                                     Wollastonite.sup.8  8.97                                                      Pentaerythritol     3.98                                                      Calcium Carbonate   4.08                                              Package 2:                                                                            VERSAMID 150.sup.9  45.79                                                     Nonyl phenol        13.57                                                     ATTAGEL-50          5.49                                                      Wollastonite        18.08                                                     Calcium carbonate   5.49                                                      Melamine            11.52                                                     Carbon black pigment                                                                              0.06                                              ______________________________________                                         .sup.1 This flexibilized epoxy was prepared as described in Example A.        .sup.2 This aromatic epoxy resin was prepared from bisphenol A and            epichlorohydrin. It has an epoxy equivalent weight of 190 to 192 and a        resin solids content of 100 percent. This resin is commercially available     from Shell Chemical Co.                                                       .sup.3 Commercially available from Stauffer.                                  .sup.4 Attapulgite clay was used herein as a rheology control agent. This     material is commercially available from Englehard minerals.                   .sup.5 Hydrogenated castor oil derivative was used as a rheology control      agent. This material is commercially available from NC Industries.            .sup.6 Ammonium polyphosphate having a phosphorus content of 32 percent b     weight. It is commercially available from Monsanto Corporation.               .sup.7 Commercially available as Firebrake ZB from U.S. Borax.                .sup.8 This fibrous reinforcing filler is commercially available from NYC     as NYAD G.                                                                    .sup.9 This amine curing agent has an average amine equivalent weight of      149. It is commercially available from Henkel.                           

The curable intumescent composition was prepared by mixing together2.015 parts by weight of Package 1 with 1 part by weight of Package 2.The composition was applied to a 1 foot section of a 4W13 I-beam at auniform thickness of 0.5 inch (12.7 millimeters). The coated beam wascured at ambient temperature for 16 hours and force cured for 5 days at60° C. The coated beam was then subjected to the following cold cycletest. One cycle of the test involved placing the coated beam in afreezer operating at a temperature between 0° F. (-18° C.) and -10° F.(-23° C.) for sufficient time for the steel to reach a temperaturebetween 0° F. (-18° C.) and -10° F. (-23° C.) as determined by the twothermocouples attached to the beam surface beneath the coating. (In thisparticular example, the thermocouples were not used. The beam was placedin the freezer for 16 hours). The beam was then removed from the freezerand a 50 square inch area (0.0323 square meter) of the surface warmed asshown by FIG. 1 by passing a heat gun [Model No. HG 50146, AlphaDivision of Loral Corporation, 14 amp, minimum temperature at tip 572°F. (297° C.)] a distance of (0.5 inch) 12.7 millimeters from thesurface, uniformly over the surface until the surface temperaturereached 60° C. within a 3 minute period, as determined by a thermocouplemoved about the surface. The beam was then allowed to stand at ambienttemperature for at least 2 hours.

The beam was able to withstand 29 cycles without cracking. After 30cycles some cracking was observed.

The curable composition, prepared and mixed as above, was also testedfor burn properties. The composition was applied to a 9 inch×9 inch×1/2inch (22860 mm×22860 mm×12.7 mm) steel plate having two thermocouplesembedded in it such that the top, bottom, and sides were uniformlycovered with a 0.3 inch (762 mm) coating. The plate was allowed to curefor 24 hours at room temperature followed by 24 hours at 140° F. (60°C.) and then burned in a gas fired furnace according to ASTM-E119(UL-263). The variable measured was the length of time required for thesteel to reach a temperature of 1000° F. (538° C.). The test wasconcluded when the steel reached this temperature [The temperature ofthe steel was measured by each of the thermocouples. When more than onethermocouple was utilized the average of all the thermocouples was takenwith the proviso that each individual thermocouple cannot exceed atemperature of 1200° F. (649° C.).]

The following data was obtained:

Thermocouple 1: 58:55 (minutes:seconds) to reach a temperature of 1000°F. (538° C.)

Thermocouple 2: 59:27 to reach a temperature of 1000° F. (538° C.)

The average time required to reach the conclusion of the test was 59:16.The resultant char was hard, exhibited good expansion, and had smallround cells. The control plate was identical to the coated plate in allrespects except that it was not coated with the curable composition. Theuncoated 9 inch×9 inch×1/2 inch steel plate required 13 minutes to reacha temperature of 1000° F. (538° C.).

The curable composition was also burned in a gas fired furnace accordingto UL1709 conditions. This is a rapid rise fire test in which thefurnace temperature reaches 2000° F. in 5 minutes. The furnace ismaintained at 2000° F. for the duration of the test. A 9"×9"×1/2" platewith the curable composition was prepared as described above. The coatedplate was allowed to cure for 16 hours at room temperature and 2 hoursat 140° F. (60° C.). The sample was burned according to UL1709. Thevariable measured was the length of time required for the steel to reacha temperature of 1000° F. (538° C.). The test was concluded when thesteel reached this temperature. [The temperature of the steel wasmeasured by each of the thermocouples]. When more than one thermocouplewas utilized, the average of all the thermocouples was taken with theproviso that each thermocouple can not exceed a temperature of 1200° F.(648° C.).

The following data was obtained:

Thermocouple 1: 35:36 (minutes:seconds) to reach a temperature of 1000°F. (538° C.)

Thermocouple 2: 37:38 to reach a temperature of 1000° F. (538° C.)

The average time to reach a temperature of 1000° F. (538° C.) was 36:37.The resultant char was hard, exhibited good expansion and has smallround cells. The control plate was identical to the coated plate exceptthat it was not coated with the curable composition. The uncoated9"×9"×1/2" steel plate required 4 minutes and 8 seconds to reach atemperature of 1000° F. (538°).

The coated I-beam which was subjected to the cold cycle test was thenburned in a gas fired furnace according to UL1709 as described above.This I-beam did not contain thermocouples prior to application of thecoating. The burn test was concluded at the end of 55 minutes and theresultant char was examined visually. The char was hard, exhibited goodexpansion and had small cells.

EXAMPLE 2

This example illustrates the preparation and testing of a flexibilizedfire protective intumescent curable composition of the presentinvention. This example demonstrates the use of a flexible materialwhich co-cures with an epoxy resin to achieve cold cycle crackresistance.

    ______________________________________                                                                Parts by Weight                                       Ingredients             (grams)                                               ______________________________________                                        Package 1:                                                                            EPON 828            11.86                                                     Urethane Acrylate.sup.13                                                                          29.63                                                     Tris(2-chloroethyl) phosphate                                                                     9.70                                                      PHOS-CHEK-P-30      2.87                                                      Zinc borate         10.91                                                     Calcium carbonate   16.17                                                     Melamine            2.16                                                      ATTAGEL-50          1.08                                                      Wollastonite        8.62                                                      ZEEOSPHERES.sup.14  6.98                                                      Carbon black pigment                                                                              0.02                                              Package 2:                                                                            Nonyl phenol        62.07                                                     Triethylene tetramine                                                                             37.93                                             ______________________________________                                         .sup.13 Urethane acrylate was prepared in resin Example B.                    .sup.14 ZEEOSPHERE 800 is a silicaalumina hollow sphere with an average       particle size of 30 microns available from ZEELAN Industries, Inc.       

The composition was prepared by mixing together 12.793 parts by weightof Package 1 with 1 part by weight of Package 2. The composition wasuniformly applied at a thickness of 0.5 inch (12.7 millimeter) to a 10inch (0.254 meter) length of a 4W13 I-beam. The coated beam was allowedto cure at ambient temperature for 16 hours, then force cured at 140° F.(60° C.) for 5 days. The Shore D hardness of the coating was 52. Thecoated beam was then subjected to the cold cycle test as describedabove.

The beam was subjected to 27 cycles of the cycle test before the cycletesting was terminated. After 27 cycles no cracking had occurred.

The coated I-beam which had been subjected to the cold cycle test wasthen burned in a gas fired furnace according to UL1709 conditions asdescribed in Example 1.

The following data was obtained:

Thermocouple 1: 38:18 (minutes:seconds) to reach a temperature of 1000°F. (538° C.)

Thermocouple 2: 40:40 to reach a temperature of 1000° F. (538° C.)

The average time to reach the conclusion of the test was 39:29. Theresultant char was hard and exhibited much expansion and a variable chardensity. The control I-beam was identical to the coated beam in allrespects except that it was not coated with the curable composition. Theuncoated 10" 4W13 I-beam required 3 minutes and 40 seconds to reach atemperature of 1000° F. (538° C.).

EXAMPLE 3

This example illustrates the preparation and testing of a flexibilizedfire protective intumescent curable composition of the presentinvention. This example demonstrates the use of a flexible epoxy curingagent to achieve cold crack resistance.

    ______________________________________                                                                Parts by Weight                                       Ingredients             (grams)                                               ______________________________________                                        Package 1:                                                                            EPON 828            23.21                                                     Tris(2-chloroethyl) phosphate                                                                     12.74                                                     PHOS-CHEK-P-30       3.76                                                     Zinc borate         14.32                                                     Calcium carbonate   21.23                                                     Melamine             2.83                                                     ATTAGEL-50           1.42                                                     Wollastonite        11.32                                                     ZEEOSPHERES          9.15                                                     Carbon black pigment                                                                               0.02                                             Package 2:                                                                            Nonyl phenol        15.34                                                     VERSAMID 150        27.99                                                     JEFFAMINE D-2000.sup.15                                                                           56.67                                             ______________________________________                                         .sup.15 JEFFAMINE D2000 is an amine terminated polypropylene glycol of        approximately 2,000 molecular weight commercially available from              Wilmington Chemical Co.                                                  

The intumescent composition was prepared by mixing together 2.41 partsby weight of Package 1 with 1 part by weight of Package 2. Thecomposition was uniformly applied at a thickness of 0.5 inch (12.9millimeter) to a 4W13 I-beam which was 10 inches long. The coated beamwas allowed to cure at room temperature for 16 hours then heat aged at140° F. (60° C.) for 5 days. The Shore D hardness of the coating was 46.The coated beam was then subjected to the cold cycle test as describedabove.

The beam was subjected to 27 cycles of the test before cycle testing wasterminated. After 27 cycles no cracking had occurred.

The coated I-beam which had been subjected to the cold cycle test wasthen burned in a gas fired furnace according to UL1709 conditions asdescribed in Example 1.

The following date was obtained:

Thermocouple 1: 44:53 (minutes:seconds) to reach a temperature of 1000°F. (538° C.)

Thermocouple 2: 47:27 to reach a temperature of 1000° F. (538° C.)

The average time to reach the conclusion of the test was 46:10. Theresultant char was hard, exhibited good expansion and had small roundcells.

What is claimed is:
 1. A substrate which demonstrates a reduced rate oftemperature rise when it is subjected to fire conditions, characterizedby having applied on the substrate surface a curable composition whichwhen exposed to fire conditions intumesces, said compositioncomprising:(a) an epoxy functional adduct of a flexible acid functionalpolyester with a polyepoxide; (b) a curing agent adapted to cure theepoxy functional adduct; and (c) an additive component comprising amixture of materials adapted to provide a source of(i) zinc, (ii) boron,(iii) phosphorus, and (iv) an expansion gas upon thermal decomposition,said composition being capable of forming a carbonaceous char uponexposure to heat or flame, with the proviso that the cured, unburnedcomposition has sufficient flexibility that it passes at least 10continuous cycles of a cold cycle test without cracking when thecomposition is applied at a thickness of 0.5 inch (12.7 millimeters) toa 10 inch (0.254 meter) section of a 4W13 I-beam having twothermocouples attached to the surface, allowed to cure at ambienttemperature for 16 hours, force cured for 5 days at about 60° C. andsubjected to the cold cycle test wherein for one cycle the beam isplaced in a freezer operating at a temperature between about 0° F. (-18°C.) and about -10° F. (-23° C.) for sufficient time for the steel toreach a temperature between about 0° F. (-18° C.) and about (-10° F.) -23° C. as determined by the two thermocouples attached to the surface ofthe beam beneath the coating, removed from the freezer and a 50 squareinch area (0.0323 square meter) of the surface warmed by passing a heatgun, 14 amps, minimum temperature at tip 500° F. (260° C.) at a distanceof 0.5 inch (12.7 millimeter) from the surface, uniformly over thesurface until the surface temperature reaches 110° F. (43° C.) within a3 minute period, as determined by a thermocouple moved about thesurface, and allowed to stand for at least 2 hours at ambienttemperature.